1. Field of the Invention
This invention relates to a cutting apparatus, in particular a flat saw, with variable cutting depth.
2. Description of the Related Art
Flat sawsxe2x80x94such as, for example, of the type BFS 100 from Wacker-Werkexe2x80x94are used for producing joints in hardened concrete, asphalt, tiles, etc. For this purpose, a diamond-set cutting disc, for example, is rotationally driven by a drive which is fastened on a chassis and thus can easily be moved over the subsurface into which the joint is to be cut. In the process, the cutting depth, i.e. the depth with which the cutting disc penetrates into the material to be worked, must be capable of being set with great precision in order to obtain a joint having a desired cross section.
For this purpose, flat saws having chassis are known in which a front wheel axis is fastened to a link pivotable relative to the main frame. Since the front wheels are located in the vicinity of the cutting disc, variable plunging of the cutting disc into the material to be cut is obtained by a pivoting movement of the link.
For the adjustment of the link, i.e. for the adjustment of the relative movement between the main frame and the link, two methods are known on the one hand, the link can be pivoted relative to the main frame by means of a spindle actuated by hand crank. Alternatively, a lever linkage with latching can be provided.
In the first solution, a relatively high setting accuracy with small operating forces can be achieved. However, in order to lift out the cutting disc or plunge it in, numerous turns of the hand crank are necessary, which increases the working time. The setting and repetitive accuracy also depends on the care of the operator, who has to count the number of crank turns or take corresponding readings.
The second solution, on account of the discrete latching positions, offers good repetitive accuracy and rapid lifting or plunging of the cutting disc. On account of the predetermined latching positions, however, the setting possibilities are limited, so that joints having any desired cutting depth cannot be produced. In addition, it is often a problem for the user in aggravated environmental conditions to find the desired latching position.
U.S. Pat. No. 4,953,523 discloses a cutting apparatus according to the preamble of Patent claim 1. Furthermore, this cutting apparatus has a quick-unlocking mechanism which is in engagement with the fine-adjustment device in a releasable manner. When the quick-unlocking mechanism is triggered, the cutting disc is set back into a transport position by the effect of a pneumatic spring.
The object of the invention is to specify a cutting apparatus in which the disadvantages known from the prior art can be avoided.
The object is achieved according to the invention by a cutting apparatus having the features of Patent claim 1. Advantageous developments of the invention can be gathered from the dependent claims.
A cutting apparatus according to the invention, in particular a flat saw, has travel gear for moving the cutting apparatus on a subsurface, a cutting disc which can be rotationally driven by a drive, a supporting frame supporting the cutting disc and the drive, an underframe fastened to the supporting frame in a movable manner and supporting at east at least one part of the travel gear, and an adjusting arrangement for adjusting the relative position of underframe and supporting frame, the adjusting arrangement having a fine-adjustment device for adjusting any desired relative positions within a certain region, and the adjusting arrangement having a coarse-adjustment device for adjusting at least two discrete relative positions and the fine-adjustment device superimposing the effect of the coarse-adjustment device in at least one of the discrete relative positions.
The advantages of the two known arrangements are therefore combined by the invention. In principle, the cutting-depth setting is effected by the coarse-adjustment device, which, however, expediently has only two latching positions, namely a transport position, in which the cutting disc does not engage in the material to be cut, and a cutting position. In the cutting position, the effect of the fine-adjustment device comes to bear, by means of which the cutting disc can be set precisely to the desired cutting depth.
Due to the fact that only two discrete relative positions are possible for the coarse-adjustment device, operating errors due to inadvertent setting of intermediate positions can be avoided. If the fine-adjustment device has been set once merely at the start of an operation, a high repetitive accuracy of the cutting depth, even if work is interrupted repeatedly, can be achieved solely by subsequent actuation of the coarse-adjustment device. Very quick lifting and plunging of the cutting disc is possible by means of the coarse-adjustment device.
In a preferred embodiment of the invention, the underframe is pivotable relative to the supporting frame and supports a part of the travel gear. In particular, the underframe supports a front axle of the travel gear, whereas the supporting frame holds the rear axle of the travel gear. As a result, the entire frame can be made very light and compact.
If the fine-adjustment device also superimposes the effect of the coarse-adjustment device in the transport position, the cutting depth can already be preset by means of a corresponding indicating device or scale without it being necessary for the cutting disc to have penetrated into the material to be cut.
In a preferred embodiment of the invention, the coarse-adjustment device is formed by a latching device and the fine-adjustment device is formed by a spindle device. As a result, the requirements with regard to robustness on the one hand the precision on the other hand can be optimally fulfilled.
It is especially advantageous in this case if the spindle device carries the latching means or latching elements of the latching device, since the effects of the coarse- and fine-adjustment devices can readily be superimposed as a result.
Another advantageous development of the invention has a spring device which prestresses the underframe relative to the supporting frame and by means of which the operator can adjust the coarse-adjustment device between the discrete relative positions with relatively small operating forces.